This invention relates to an exchange for an integrated services digital network (ISDN).
Generally, the exchange is connected through private or public lines to an integrated services digital network which includes a plurality of terminal units, such as a speech unit, a facsimile unit, and a data processing unit. An incoming call is sent from the integrated services digital network to the exchange through a particular one of the public lines. In the manner known in the art, particular ones of the terminal units are preassigned to the incoming call in a system which is generally called a direct in line (DIL) system or a direct in termination (DIT) system.
The integrated services digital network carries out various kinds of communication, for example, speech communication, data communication, and packet communication. The kind of communication is represented by bearer capability in the integrated services digital network. The communication can be carried out through a single one of the public lines. Accordingly, it is preferable that the exchange should automatically distribute the incoming call to the particular terminal unit by or in relation to the kind of communication.
A conventional exchange comprises a control portion for controlling the incoming call. During the daytime, the control portion may select, as a first selected terminal unit, one of the particular terminal units. Receiving the incoming call through the particular line, the exchange seeds the incoming call to the first selected terminal unit.
At night, the control portion may select, as a second selected terminal unit, another of the particular terminal units. Receiving the incoming call through the particular line, the exchange sends the incoming call to the second selected terminal unit.
It is, however, impossible in the conventional exchange to distribute the incoming call to the particular terminal units in relation to the kinds of communication. In other words, the conventional exchange carries out its operation regardless of the kind of the communication.